Hello Gaby and Technet


Gabriela Bogdan wrote in response to my Technet message asking for gold
density values for Hard and soft
golds:

   Gerry,
I am also interested. Please resend any information to me too. I think
that
I could use it in my XRF applications . But, what do you think about the
problem of different
suppliers with different bath
formulations and processes?
Bye,
Gaby


Gaby

I only received two responses. One response was from a chemical supplier
who did not supply any information other than urging caution with
interpreting values I would receive. The other response was from an old
friend in the plating chemistry field. He supplied the values of 17.5
g/cc for the hard gold plate and 19.3 g/cc for the pure gold (i.e.
immersion and soft gold plate). The purpose for my question was to
obtain data to get a baseline for help in determining the correct gold
thickness for a special board I'm designing which will have gold for
multiple purposes (connector contact AND solderable).

If you recall a rather lengthy post I made on the subject of gold and
gold thickness, I forgot to mention an item that had a major impact on
thickness. I called this item "density correction". I remember measuring
gold thickness by beta backscatter and XRF techniques and had noticed
(via hi mag SEM) that we always were plating more gold than that
reported by these techniques. The funny thing is that it was always off
by a constant value! It turned out that the constant was the ratio of
the gold density of the calibration standard (pure gold at 19.3 g/cc) to
the density of the "as plated" deposit (hard gold at approx. 17 g/cc).
At that time it was difficult to obtain calibration standards prepared
from "as plated" deposits as a solution to this issue, so we merely
applied the correction factor to the readings. I'm sure that things are
radically different today with  the more modern equipment and
calibration techniques.

To your second question. In my own opinion (and I could be wrong) I
don't think the variation in plating density between board shops will be
significant enough to worry about. I would be more concerned with
deposit thickness AND quality.


Regards

Gerry

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